Mechanism of 5-hydroxytryptamine induced calcium signaling in cultured rat stomach fundus smooth muscle cells / 中国药理学通报

ABSTRACT

AIM To get an insight into intracellular signaling steps, a very early step in the signaling cascade, the biphasic Ca 2+ elicited by 5 HT in rat stomach fundus smooth muscle cells was investigated. METHODS Cells were cultured and loaded with Fluo 3 AM. [Ca 2+ ] i was measured by fluorescent intensity (FI) in each cell with confocal microscopy. RESULTS The resting FI level of SFSMC was 264?15. Stimulation of SFSMCs by 5 HT produced an elevation of [Ca 2+ ] i; Depletion of external Ca 2+ by addition of EGTA led to a significant attenuation of [Ca 2+ ] i change induced by 5 HT; Pre treatment of SFSMCs with ryanodine (10 ?mol?L -1 , 5 min) in D Hanks, the effect of 5 HT was completely inhibited; The stimulation of SFSMCs by 5 HT was partly attenuated by miaserin(10 ?mol?L -1 ), however, L type Ca 2+ channel antagonist lacidipine and G protein inhibitor NEM completely abolished the increase of [Ca 2+ ] i mediated by 5 HT; 5 HT mediated Ca 2+ release was reduced by phospholipase C specific inhibitor compound 48/80(1 2 ?g?ml -1 ); When protein kinase C was activated by phorbol 12 myristate 13 acetate (PMA 0 1 ?mol?L -1 , 5 min) the effect of 5 HT was inhibited, and the inhibitory effect of PMA was reversed by D sphingosine, a PKC inhibitor. CONCLUSION Our data suggest that G protein coupled 5 HT 2B receptor in the rat stomach fundus modulates 5 HT stimulated Ca 2+ increase, and it is coupled to calcium influx through L type calcium channels, and also intracellular calcium release by the opening of ryanodine receptor. The 5 HT 2B receptor mediated signal of 5 HT is transduced by PLC and PKC.